In recent, semiconductor memory devices continue to approach to high integration and high speed with development of technologies and are employed and used in various products including large home electric appliances and small mobile products.
These semiconductor memory device is made up of a plurality of memory cells in which data is recorded, and the data is read out as ‘1’ or ‘0’ depending on an amount of charge accumulated in the memory cell. Upon read operation, the data stored in the memory cell is transferred through a bit line, a local line and a global line in turn, and is then outputted to an outside through a data pad. In order to prevent the data from being lost during passing through the various transfer paths, a sense amplifier is provided between respective lines to maintain data level. This sense amplifier is provided on the bit line, the local line and the global line, respectively.
Among these, a sense amplifier that senses the data inputted through the local line and transfers it to the global line will be exemplary described herein. In general, the sense amplifier receives and senses the data through a first line pair including a first line and a first inverted line and outputs it to a second line. At this time, in order for the sensing operation of the sense amplifier, a potential difference in the first line pair must be more than a predetermined level (hereinafter, referred to as ‘sensing level’). The sense amplifier performs the sensing operation properly when the potential difference in the first line pair is more than the sensing level. On the contrary, an error occurs in the sensing operation when the potential difference in the first line pair is smaller than the sensing level. In other words, the sense amplifier cannot properly sense the data transferred through the first line pair and may output the data to the second line with the level of the data being inverted when the potential difference between the first line pair is smaller than the sensing level of the sense amplifier.